1. Field of the Invention
The present invention is related to a capacitive touch screen, and more particularly, a capacitive touch screen that avoids misjudgment due to water thereon.
2. Description of the Prior Art
A conventional mutual capacitive sensor includes an insulating surface layer, a first conductive layer, a dielectric layer, a second conductive layer. The first conductive layer and the second conductive layer have a plurality of first conductive strips and a plurality of second conductive strips, respectively. Each of these conductive strips can be made up by a plurality of conductive pads and connecting lines connected to the conductive pads in series.
In the process of mutual capacitive detection, one of the first conductive layer and the second conductive layer is driven, while the other of the first conductive layer and the second conductive layer is detected. For example, a driving signal is sequentially provided to each first conductive strip, and corresponding to each first conductive strip provided with the driving signal, signals from all of the second conductive strips are detected, which represent capacitive coupling signals at the intersections between the first conductive strip provided with the driving signal and all the second conductive strips. As a result, capacitive coupling signals at the intersections between all the first and second conductive strips are obtained to form an image of capacitive values.
The image of capacitive values at the time when there is no external touches is obtained as a reference. By comparing the difference between the reference image and the image of capacitive values later detected, the touch or approach of an external conductive object can be determined, and furthermore, the position touched or approached by the external conductive object can be determined.
However, if a conductive substance crosses over at least two conductive strips on the insulating surface layer, even when there is no touch or approach by any external conductive object, the image of capacitive values may change as a result of capacitive coupling between the conductive substance and the conductive strips, leading to misjudgments. For example, a water stain crossing more than two conductive strips on the insulating surface layer may cause changes in the image of capacitive values, and may be mistaken as the pressing of a finger.
From the above it is clear that prior art still has shortcomings. In order to solve these problems, efforts have long been made in vain, while ordinary products and methods offering no appropriate structures and methods. Thus, there is a need in the industry for a novel technique that solves these problems.